Resist composition and patterning process

Abstract

A resist composition comprising a base polymer and an acid generator containing a sulfonium salt having an iodized benzene ring offers a high sensitivity, minimal LWR and improved CDU independent of whether it is of positive or negative tone.

The invention claimed is: 
     
       1. A resist composition comprising an acid generator containing a sulfonium salt having the formula (1): 
       
         
           
           
               
               
           
         
         wherein R 1  and R 2  are each independently a single bond or a C 1 -C 20  divalent aliphatic hydrocarbon group which may contain an ether bond, ester bond or hydroxyl,
 L 1  is an ester bond, ether bond or amide bond, 
 L 2  and L 3  are each independently a single bond, ester bond, ether bond or amide bond, 
 R 3  is hydroxyl, carboxyl, nitro, cyano, fluorine, chlorine, bromine, amino, or a C 1 -C 20  alkyl, C 1 -C 20  alkoxy, C 2 -C 20  acyloxy, C 2 -C 20  alkoxycarbonyl or C 1 -C 4  alkylsulfonyloxy group, which may contain fluorine, chlorine, bromine, hydroxyl or amino, or —NR 3A —C(═O)—R 3B  or —NR 3A —C(═O)—O—R 3B , wherein R 3A  is hydrogen or a C 1 -C 6  alkyl group which may contain halogen, hydroxyl, C 1 -C 10  alkoxy, C 2 -C 10  acyl or C 2 -C 10  acyloxy, R 3B  is a C 1 -C 16  alkyl, C 2 -C 16  alkenyl or C 6 -C 12  aryl group, which may contain halogen, hydroxyl, C 1 -C 10  alkoxy, C 2 -C 10  acyl or C 2 -C 10  acyloxy, 
 R 4  is hydroxyl, carboxyl, nitro, cyano, fluorine, chlorine, bromine, iodine, amino, or a C 1 -C 2 alkyl, C 1 -C 20  alkoxy, C 2 -C 20  acyloxy, C 2 -C 20  alkoxycarbonyl or C 1 -C 4  alkylsulfonyloxy group, which may contain fluorine, chlorine, bromine, iodine, hydroxyl, amino or ether bond, 
 R 5  is a C 1 -C 20  monovalent hydrocarbon group which may contain a heteroatom, in case of r=1, two R 5  may be the same or different and may bond together to form a ring with the sulfur atom to which they are attached, 
 X −  is a non-nucleophilic counter ion, 
 m is an integer of 1 to 5, n is an integer of 0 to 3, the sum of m+n is 1 to 5, p is 0 or 1, q is an integer of 0 to 4, and r is an integer of 1 to 3. 
 
       
     
     
       2. The resist composition of  claim 1  wherein m is an integer of 2 to 5. 
     
     
       3. The resist composition of  claim 1  wherein the non-nucleophilic counter ion is a fluorinated sulfonate, fluorinated imide or fluorinated methide ion. 
     
     
       4. The resist composition of  claim 1 , further comprising an organic solvent. 
     
     
       5. The resist composition of  claim 1 , further comprising a base polymer. 
     
     
       6. The resist composition of  claim 5  wherein the base polymer comprises recurring units having the formula (a1) or recurring units having the formula (a2): 
       
         
           
           
               
               
           
         
         wherein R A  is each independently hydrogen or methyl Y 1  is a single bond, phenylene group, naphthylene group, or C 1 -C 12  linking group containing an ester bond or lactone ring, Y 2  is a single bond or ester bond, R 11  and R 12  each are an acid labile group, R 13  is fluorine, trifluoromethyl, cyano, C 1 -C 6  alkyl, C 1 -C 6  alkoxy, C 2 -C 7  acyl, C 2 -C 7  acyloxy, or C 2 -C 7  alkoxycarbonyl group, R 14  is a single bond or a C 1 -C 6  straight or branched alkanediyl group in which some carbon may be replaced by an ether bond or ester bond, a is 1 or 2, b is an integer of 0 to 4, the sum of a+b is 1 to 5. 
       
     
     
       7. The resist composition of  claim 6  which is a chemically amplified positive resist composition. 
     
     
       8. The resist composition of  claim 5  wherein the base polymer is free of an acid labile group. 
     
     
       9. The resist composition of  claim 8  which is a chemically amplified negative resist composition. 
     
     
       10. The resist composition of  claim 5  wherein the base polymer further comprises recurring units of at least one type selected from the formulae (f1) to (f3): 
       
         
           
           
               
               
           
         
         wherein R A  is each independently hydrogen or methyl,
 Z 1  is a single bond, phenylene group, —O—Z 11 —, —C(═O)—O—Z 11 — or —C(═O)—NH—Z 11 —, Z 11  is a C 1 -C 6  alkanediyl group, C 2 -C 6  alkenediyl group, or phenylene group, which may contain carbonyl, ester bond, ether bond or hydroxyl, 
 Z 2  is a single bond, —Z 21 —C(═O)—O—, —Z 21 —O— or —Z 21 —O—C(═O)—, Z 21  is a C 1 -C 12  alkanediyl group which may contain carbonyl, ester bond or ether bond, 
 Z 3  is a single bond, methylene, ethylene, phenylene, fluorinated phenylene, —O—Z 31 —, —C(═O)—O—Z 31 — or —C(═O)—NH—Z 31 —, Z 31  is a C 1 -C 6  alkanediyl group, C 2 -C 6  alkenediyl group, phenylene group, fluorinated phenylene group, or trifluoromethyl-substituted phenylene group, which may contain carbonyl, ester bond, ether bond or hydroxyl, 
 R 21  to R 28  are each independently a C 1 -C 20  monovalent hydrocarbon group which may contain a heteroatom, any two of R 23 , R 24  and R 25  or any two of R 26 , R 27  and R 28  may bond together to form a ring with the sulfur atom to which they are attached, 
 A is hydrogen or trifluoromethyl, and 
 M −  is a non-nucleophilic counter ion. 
 
       
     
     
       11. The resist composition of  claim 1 , further comprising a surfactant. 
     
     
       12. A process for forming a pattern comprising the steps of applying the resist composition of  claim 1  onto a substrate, baking to form a resist film, exposing the resist film to high-energy radiation, and developing the exposed resist film in a developer. 
     
     
       13. The process of  claim 12  wherein the high-energy radiation is ArF excimer laser radiation of wavelength 193 nm or KrF excimer laser radiation of wavelength 248 nm. 
     
     
       14. The process of  claim 12  wherein the high-energy radiation is EB or EUV of wavelength 3 to 15 nm.